Cyclopentenolones of formula I wherein R1 is hydrogen or methyl, and R2 is C1-C10 alkyl, C2-C10 alkenyl, C2-C10 alkynyl, C1-C4 haloalkyl, a C5-C9 hydroxy aliphatic hydrocarbon moiety which may be optionally protected on the terminal hydroxyl group thereof, or a C5-C9 fatty acid residue which may be optionally protected on the terminal carboxyl group thereof, are important as the intermediates of drugs, agricultural chemicals or other active products
These cyclopentenolones are useful as the important alcohol components in a group of ester compounds, commonly called “synthetic pyrethroids,” having excellent insecticidal activity, and they are also useful as the intermediates of prostaglandin derivatives which serve as drugs.
For example, the compound of formula II below, an ester of 4-hydroxy-3-methyl-2-(2-propynyl)cyclopent-2en-1-one with 2,2,3,3-tetramethylcyclopropanecarboxylic acid, is an excellent insecticide having very strong knockdown activity and mortal activity (see, e.g., JP-B 50-15843/1975). 
The cyclopentenolones of formula I include two kinds of optical isomers because they have an asymmetric carbon atom at position 4. In the case of synthetic pyrethroids containing such optical isomers as the alcohol components, it is well known that the difference in optical isomerism between these alcohol components makes a great difference in their insecticidal effects. For example, the compound of formula II above has been found to exhibit several times as excellent insecticidal activity in the case of an ester of (S)-4-hydroxy-3-methyl-2-(2-propynyl)cyclopent-2-en-1-one as in the case of an ester of the corresponding (R)4-hydroxy-3-methyl-2-(2-propynyl)cyclopent-2-en-1-one.
Furthermore, similar optically active cyclopentenolones of formula I, such as 4-hydroxy-2-(7-hydroxyheptyl)-2-cyclopentenone, 4-hydroxy-2-(6-methoxycarbonylhexyl)-2-cyclopentenone and 4hydroxy-2-(2-propenyl)-2-cyclopentenone, are useful as the intermediates of prostaglandin derivatives which serve as drugs.
For these reasons, there has been a great demand for the development of a method for separating and obtaining the optical isomers of cyclopentenolones of formula I as the intermediates of drugs, agricultural chemicals or other active products in an industrially favorable manner. In addition, for this purpose, in order to prepare a microorganism, for example, by a gene engineering technique, which microorganism can produce an excellent esterase capable of acting upon an organic carboxylic acid ester of a cyclopentenolone of formula I for asymmetric hydrolysis of the ester, the search of a gene coding for such an esterase has also been eagerly desired.